Wireless transmission of speech



E. ,C HANSUN. WIRELESS TRANSMISSION OF SPEECHW.

APPLICATION HLED JUNE 18, 291i.

Patented May 25, 192mm RECI/V/A/G TRAM M/TT/NG AMPL/ /ER W wwmko z WWW UNITED sTATEs EARL C. HA NSON, OF WASHINGTON, DISTRICT OF COLUMBIA.

WIRELESS TRANSMISSION OF SPEECH.

Specification of Letters Patent.

Patented-Ma 25, 1920;

Application filed June 18, 1917. Serial No. 175,456.

T all whom it may concern Be it known that I, EARL C. Hanson, of

- \Vashington, District of Columbia, have in vented certain new and useful Improvements in the \Vireless Transmission of Speech, of which the following is a specification.

This invention relates to the transmission of articulate speech through natural media, without connecting wires or other conducting members between the transmitting and receiving stations. It differs radically from the well known radio systems in that it em- 'PlOYS only waves at audio, or voice-frequency, rather than waves of radio fre quency. This distinction between audio or voice-frequency and radio frequency is now well recognized by radio engineers, and others skilled in the electric arts and is clearly pointed out in the specification forming part of my prior United States Patent No. 1,315,197, dated September 2d, 1919.

Said rior patent describes and claims certain improvements in a wireless audio frequency receiving station, in which the es sential e e amplifying the audio frequency energy. This invention has made practical the Edison and Dolbear systems of Wireless communication in that it rendered possible, for the first time, the maintenance of reliable communication over distances heretofore known to be impossible by the use of said systems. The present invention relates, primarily, to certain improvements in the transmitting circuits employed in systems of the character above referred to, and is based upon the discovery that if a vacuum tube relay, of sufficiently high power, is inserted in the transmitting circuit it will deliver to the antenna circuit voice-frequency energy of such augmented strength as to materially increase the distance over which reliable te1ephonic communication may be'maintained.

At the transmitting station I employ a transformer, having in its primary circuit an amplifier the input of whichis voice controlled through the instrumentality of a telephone transmitter. The secondary terminals of the transformer are connected to an antenna circuit.

At the receiving station there may be an amplifier and telephone receiver connected inent is a vacuum tube relay for.

" former, the secondary terminals being to said amplifier, the input terminals of this amplifier being connected to the antenna and antenna, circuit.

The annexed drawing illustrates my invention diagramatically. In said drawing telephone transmitter M is shown as connected to th e input terminals E and F of the trans mitting amplifier D. The feeble voice currents controlled by the telephone transmitter M are amplified many hundreds of times by the amplifier D. This amplified current is conducted to the primar of the transformer I from the termina s Y and W of the transmitting amplifier D. The second ary terminals of the transformer I are connected to an antenna circuit A.-G. The switch H is used to connect either the transmitting or receiving apparatus to the antenna circuit. The receiving apparatus consists of an amplifier X and telephone receiver T. The input of the am lifier is' connected to the antenna circuit. he telephone receiver T is actuated by varying currents received and amplified by X. The amplifier X may consist of, for example, the well known De Forest audion amplifier. The transmitting amplifier D may be of the high power type, using the Pliotron tube as developed in the research laboratory of the General Electric Company at Schenectady, New York.

IVhen switch H is placed on point J the transmitting ap aratus is connected to the antenna circuit When switch H is placed on K the receiving apparatus is connected to the antenna circuit.

The use of an amplifier at the receiving station where oscillations of only low fre quency are employed at the transmitting station is, I believe,ca new and useful improvement in such a system of speech trans- IIHSSIOII.

The use at a transmitting station, of a voice controlled amplifier, of the type employing Pliotron tubes, controlling the current flow in the primary circuit of atransconnected to the earth and antenna and thereby producing only low frequency electro-static fields, is a very important feature of my invention. y

I do not wish to be limited to the particular embodiment of my invention which I have disclosed herein inasmuch as many modifications may be made herein by those thereof, a transformer having its primary skilled in the art Without departing from connected with the output circuit of said the spirit of my invention: relay and its secondary connected to an an- I claim: 7 tenna circuit.

5 In a Wireless transmitting station, means In testimony whereof I have hereunto set 15 for transmitting energy havinga frequency. my hand. not in excess of speech frequency through natural media, including a voice controlled lVitnesses: input circuit, a .vacuum'tube relay connected RAYMOND B. RQNEY,

10 with said circuit for amplifying the energy r THERON T. Tnrrms'rr.

EARL c. HANSON. 

